Chapter 7: Cellular Respiration Organic molecules + O 2 CO 2 + H2O + EnergyPart 1: Aerobic Respiration (4 Steps of Glucose Metabolism)I. Step 1: Glycolysis (Fig. 7.4) A. Performed by almost all organismsB. Doesn’t require O2C. Occurs in cytosolD. Breaks glucose in half (C6 2 C3)1. (1 glucose2 pyruvate)E. Net gain of 2 ATP & 2 (NADH + H+)F. 10 steps in 3 phases: 1. Energy Investment Phase a. Glucose + Enzyme + 2ATP 6-Carbon compound + 2 ADP2. Cleavage Phase a. 6-Carbon compound 2 G3P3. Energy Liberation Phase a. 2 G3P 2 molecules ofpyruvate + 4 ATP + 2 NADH:G. NADH & Redox Reactions1. NAD + + 2e - + H + NADH (redox rxn.)a. NAD+ reduced (gains energy);Pyruvate oxidized (losesenergy)b. NADH is an “energyintermediate”2. Redox Reactions a. Oxidized molecules tend to lose Hi. Tend to have C-O bonds, not C-H nondsii. Follow H to follow electronsH. ATP in glycolysis is generated by an enzyme (substrate level phosphorylation) 1. Phosphoenolpyruvate (1 phosphorous) and ADP combine on an enzyme to form ATP + pyruvate I. Pyruvate is transported into mitochondria & breakdown continues—II. Step 2: Pyruvate Breakdown (Acetyl Co-A Synthesis) ( Fig. 7.6) A. Pyruvate dehydrogenase removes CO2 from3-C pyruvateB. 2-C acetyl combines with CoAC. Per pyruvate: 1 acetyl CoA, 1 NADH, 1 CO2III. Step 3: Citric Acid Cycle (Krebs Cycle) (Fig. 7.7) A. Each acetyl group is oxidized to 2 CO2B. Acetyl (2-C) removed & attatched to oxaloacetate (4-C Citrate (6-C)C. Cycle releases 2 CO2, 1 ATP, 3NADH, 1 FADH2D. Oxaloacetate is regeneratedE. Regenrates high energy compounds by incorporating & then breaking down acetyl group (see Fig.7.7)Breakdown of 1 glucose (so far):Process ATP NADH HADH2CO2OtherGlycolysis 2 2 -- -- 2 PyruvatePyruvate breakdown -- 2 -- 2 2 Acetyl-CoAKrebs 2 6 2 4 --Total 4 10 2 6 --IV. Oxidative Phosphorylation (Electron Transport Chain + ATP Synthesis) A. Uses NADH & FADH2 to make ATPB. “Oxidative Phosphorylation” includes the ETC & phosphorylation of ADP via ATP Synthase1. Electron Transport Chain a. Composed proteins or small organic moleculesb. Accept & release electrons in a series of redox reactionsc. Electrons lose energy as they move through ETCd. Electron movement generates H+ electrochemical gradient (proton-motive force)C. Process of Oxidative Phosphorylation 1. NADH donates electrons to complex I; complex I accepts them & pumps H+ across membrane2. FADH2 transfers electrons to complex II3. Electrons move to CoQ (Or U, for ubiquinone), forming CoQH24. Electrons donated from CoQH2 to complex III; H+ pumped across membranea. H+ accumulating on bottom of diagram (inside) – making acidic environmentb. Protons (H+) being pumped across membrane at complex I & complex III so far5. Electrons transferred to Cc6. Electron transferred to IV. IV pumps H+ across the membrane and transfers electrons tothe final electron acceptor, an oxygen atom, resulting in H2O formation – electron transport chain endsa. Products of electron transport chain – H2O & the H+ gradient7. H+ gradient used by ATP synthase to make ATP MatrixIntermembrane SpaceV. Summary of Aerobic Eukaryotic Respiration A. NADH & FADH2 donate electronsB. Oxygen atom is the ultimate electron acceptorC. Electron movement is highly exergonicD. Complexes I, III, & IV use energy from exergonic electron movement to pump H+ into intermembrane spaceE. ATP synthase uses H+ gradient to power ATP synthesisF. Respiration breaks down fats & proteins also1. Fats & proteins enter the catabolic pathway at different placesG. Summary Diagrams:*Some prokaryotes also produce ATP through oxidative phosphorylation (useplasma membrane for ETC instead of mitochondrial membrane)Part 2: Anaerobic Respiration (Fermentation in Humans)I. Fermentation A. Breakdown of organic molecules to produce energy without any net oxidation in the systemB. May use organic or inorganic electron acceptorC. Produces less ATP than aerobic metabolismII. Fermentation in Humans A. Pyruvate (from glycolysis) + NADH + H+ lactic acid +
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